Performance optically coated semiconductor devices and related methods of manufacture

ABSTRACT

The present application disclosed various embodiments of improved performance optically coated semiconductor devices and various methods for the manufacture thereof and includes depositing a first layer of a low density, low index of refraction material on a surface of a semiconductor device, depositing a multi-layer optical coating comprising alternating layers of low density, low index of refraction materials and high density, high index of refraction materials on the coated surface of the semi-conductor device, selectively ablating a portion of the alternating multi-layer optical coating to expose at least a portion of the low density first layer, and selectively ablating a portion of the first layer of low density material to expose at least a portion of the semiconductor device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 61/007,494, filed Dec. 12, 2007, the entirecontents of which is hereby incorporated by reference in its entiretyherein.

BACKGROUND

Presently, there is ever-increasing demand for semiconductoroptoelectronic devices having spectral performances tuned for manycritical applications. For example, FIG. 1 graphically shows theresponsivity of a typical silicon-based photovoltaic detector. As shown,the silicon-based photovoltaic detector has an approximately linearspectral responsivity from about 200 nm to about 1200 nm. In contrast,FIG. 2 shows the spectral responsivity of the same photovoltaic detectortuned or otherwise configured to selectively detect a narrow wavelengthband of incident light from about 720 nm to about 820 nm.

In another example, FIG. 3 shows an example of the spectral output of alight emitting diode (LED). In contrast, FIG. 4 shows that the spectraloutput of the silicon-based LED shown in FIG. 3 may be tuned to output amore narrow spectral range. Presently, numerous applications demandprecise spectral tuning of their optoelectronic components, includingthose used for high-precision biomedical fluorescence applicationsand/or other critical measurement-and-control applications.

Numerous methods have been attempted to produce spectrally tunedoptoelectronic devices. For example, as shown in FIG. 5 one previousdevice incorporates an optically-coated glass component 5 mountedexternal of the housing 3 of the semiconductor device 1. Alternatively,FIG. 6 shows an embodiment of a device 7 having a detector device 11positioned within a device housing 9. As shown, an optically coatedglass filter device 13 is positioned within the housing 9 proximate tothe detector device 11. Typical optically-coated glass devices consistof glass or glass-like optically transparent substrates (e.g. SchottBorofloat, BK-7, fused silica, etc) having at least one multilayerthin-film optical interference coating applied thereto. For example,often the multilayer optical interference coating comprises alternatinglayers of materials having a low index of refraction and a high index ofrefraction. While numerous methods exist for producing such opticalthin-film coatings, relatively few coating processes achieve the filmstructure and density required for high-precision applications. Forexample, conventionally deposited optical thin films (e.g. thermal orelectron-beam evaporated oxide-based materials such as SiO2, HfO2.Ta2O5, etc) have micro-morphologies which are columnar and porous,allowing the absorption and desorption of atmospheric moisture. As such,the effective index of refraction of the multi-layer thin film maychange as a result of such moisture entrapment, which may result inspectral shifts and instabilities. For many critical instrumentapplications, this results in devastating losses of the opticalprecision. Alternative state-of-the-art optical coating processestherefore are geared towards densifying thin films as a means to preventsuch moisture penetration. As such, the multilayer optical interferencecoating comprises alternating layers of low index and high indexmaterials, wherein both the low and high index materials are highdensity materials. Such processes include reactive ion plating,ion-assisted electron-beam evaporation, ion-beam sputtering, magnetronsputtering, and plasma-enhanced CVD.

While current optical thin-film multilayer deposition technologies (e.g.ion plating, ion-beam sputtering, magnetron sputtering, ion-assistedelectron beam deposition, CVD, etc.) satisfy the need for creatingdensified optical coatings, a number of shortcomings have identified.For example, these processes fail to provide the ideal configuration foruse as directly deposited optical coatings upon semiconductor surfaces.More specifically, current deposition technologies produce densifiedoptical coating films having undesirable excessive film stresses, whichmay deteriorate the performance of the device. In addition, these highlydensified optical coating films are difficult, if not impossible, tofurther process (e.g. etch) once the coating is applied.

Therefore, in light of the foregoing, there is an ongoing need for amultilayer optical thin-film coating method capable of producing anoptical coating on a semiconductor wafer device or material that isenvironmentally stable, but both minimizes harmful stresses, and allowsfor a simple, non-damaging and manufacturable post-deposition etchingprocess.

SUMMARY

The present application discloses various embodiments of improvedperformance optically coated semiconductor devices and various methodsfor the manufacture thereof. Unlike prior art devices, the devicesdisclosed herein include a semiconductor wafer or body having a lowdensity, low index of refraction first layer, and a multi-layer opticalcoating applied thereto. In one embodiment, the multi-layer opticalcoating comprises alternating layers of a low density, low index ofrefraction optical material and high density, high index of refractionoptical material. Unlike prior art devices, the inclusion of lowdensity, low index of refraction materials in cooperation with highdensity, high index of refraction materials provides an optical coatedsemiconductor device which may undergo further processes withoutdegrading the performance characteristics thereof.

In one embodiment, the present application is directed to a method ofmanufacturing an optically coated semiconductor device and includesdepositing a first layer of a low density, low index of refractionmaterial on a surface of a semiconductor device, depositing amulti-layer optical coating comprising alternating layers of lowdensity, low index of refraction materials and high density, high indexof refraction materials on the coated surface of the semiconductordevice, selectively ablating a portion of the alternating multi-layeroptical coating to expose at least a portion of the low density firstlayer, and selectively ablating a portion of the first layer of lowdensity material to expose at least a portion of the semiconductordevice.

In another embodiment, present application is directed to a method ofmanufacturing an optically coated semiconductor device and includesdepositing a first layer of a low density, low index of refractionmaterial on a surface of a semiconductor device, depositing amulti-layer optical coating comprising alternating layers of lowdensity, low index of refraction materials and high density, high indexof refraction materials on the coated surface of the semiconductordevice, selectively ablating a portion of the alternating multi-layeroptical coating using a physical ablation process to expose at least aportion of the low density first layer, and selectively ablating aportion of the first layer of low density material using a controlledchemical etching process to expose at least a portion of thesemiconductor device.

In another embodiment, the present application is directed to asemiconductor device having an optical coating selectively appliedthereto and includes at least one semiconductor wafer having at least afirst surface, a first layer of low density, low index of refractionoptical material applied to at least the first surface of thesemiconductor wafer, a multi-layer optical coating applied to the firstlayer of low density, low index of refraction material, the multi-layeroptical coating comprising alternating layers of low density, low indexof refraction materials and high density, high index of refractionmaterials.

Other features and advantages of the embodiments of the improvedperformance optically coated semiconductor devices as disclosed hereinwill become apparent from a consideration of the following detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

Various improved performance optically coated semiconductor devices willbe explained in more detail by way of the accompanying drawings, wherein

FIG. 1 shows a graph of the wavelength responsivity of a typicalsilicon-based photovoltaic detector;

FIG. 2 shows a graph of the wavelength responsivity of the photovoltaicdetector of FIG. 1 tuned or otherwise configured to selectively detect anarrow wavelength band of incident light from about 720 nm to about 820nm;

FIG. 3 shows a graph of the wavelength transmission of a typicalsilicon-based light emitting diode;

FIG. 4 shows a graph of the wavelength transmission of a typicalsilicon-based light emitting diode shown in FIG. 3 selectively tuned tooutput a narrow wavelength band of light;

FIG. 5 shows a schematic of an embodiment of an optoelectronic devicehaving an optically-coated glass component mounted external of a devicebody;

FIG. 6 shows a schematic of an embodiment of an optoelectronic devicehaving an optically-coated glass component mounted within a device body;

FIG. 7 shows a side view of an embodiment of an improved semiconductordevice having a device body with a first layer of low density, low indexof refraction material applied thereto, and a multi-layer opticalcoating applied to the first layer;

FIG. 8 shows a perspective view of an alternate embodiment ofsemiconductor device having multiple detector regions formed thereon;

FIG. 9 shows a perspective view of another embodiment of semiconductordevice having multiple detector regions formed thereon;

FIG. 10 shows graphically the reflectance characteristics of the opticalcoating applied to an exemplary semiconductor device manufactured usingthe processes disclosed herein; and

FIG. 11 shows the transmittance of the optical coating applied to anexemplary semiconductor device manufactured using the processesdisclosed herein.

DETAILED DESCRIPTION

FIG. 7 shows an embodiment of an improved performance semiconductordevice. As shown, the semiconductor device 40 includes at least onesemiconductor device body 42 having at least one multilayered opticalcoating 48 applied thereto. For example, in one embodiment thesemiconductor device 40 comprises a single detector chip or deviceconfigured to detect an optical signal at a desired wavelength. In analternate embodiment, the semiconductor device 40 comprises multipledetector chips, devices, or regions formed on a semiconductor substrate(See FIGS. 8 and 9). In the illustrate embodiment, the optical coating48 is applied to a first surface 44 of the device body 42. Optionally,the coating 48 may be applied to multiple surfaces of the device body42. For example, the optical coating 48 may be selectively applied tothe first surface 44, the second surface 46, and/or both surfaces 44, 46of the device body 42.

Referring again to FIG. 7, in one embodiment the optical coating 48comprises two or more alternating layers of materials having a low indexof refraction 50 (hereinafter low index materials) and materials havinga high index of refraction 52 (hereinafter high index materials). Forexample, the low index material layer 50 may comprise silicon dioxide.In another embodiment, the low index material layer 50 may comprisealuminum oxide, silicon monoxide, magnesium fluoride, or thoriumfluoride. Similarly, a variety of materials may be used to form one ormore of the high index layers 52 of the multilayer coating 48. Forexample, in one embodiment the high index material layers 52 maycomprise niobium dioxide. Optionally, any variety of high index materiallayers 52 may be used, including, without limitation, titanium dioxide,tantalum pentoxide, hafnium dioxide, zirconium dioxide, aluminumnitride, zinc sulfide, or zinc selenide. During use, the multilayeredcoating 48 is configured transmit light having a desired opticalcharacteristic therethrough. In one embodiment, the coating 48 may beconfigured to transmit light having a desired wavelength therethough.For example, the coating 48 may be configured to transmit light having awavelength between about 475 nm and about 575 nm therethrough.Optionally, the coating 48 may be configured to transmit only lighthaving a desired polarization therethrough.

Unlike prior art devices, the low index layers 50 may be deposited on tothe semiconductor body 48 using coating methods such as resistive-sourceevaporation or conventional electron-beam deposition that achievelow-stress, low-density, porous columnar film structures. In oneembodiment, the columnar-structured low-index layers 50 are configuredto easily and quickly chemically etched. For example, the low indexmaterial layers 50 may be etched using standard non-damaginghydrofluoric acid processes. These low index layers 50, in themselves,may not provide the required hermetic-sealing (e.g. non-moistureabsorbing) properties needed for the final optical film structure.Rather, subsequently applied high index layers material layers 52deposited onto the device body 42 using proven methods such as magnetronsputtering, ion-beam sputtering, cathodic-arc deposition, ion-assistedelectron-beam deposition, or ion-plating provide the required high filmdensities capable of providing hermetic sealing. Therefore, thealternating structure of porous, low-density, low-stress low indexmaterial layers 50 together with encapsulating highly densified, highindex material layers 52 provides a final optical coating 48 that fullyprevents deleterious moisture absorption. Further, the highly densifiedhigh index material layers 52 may be configured to be etched usinghigh-energy physical methods of removal such as ion beam milling orreactive ion etching. Moreover, the inclusion of the low density lowindex material layers 50 has intrinsically very low stress. As such, thecombination of low density low index material layers 50 and highlydensified high index material layers 50, 52, respectively, hassignificantly lower stress as compared to current-art deposition methodswhich rely on highly densified low and high index materials. In oneembodiment, the individual film thicknesses of both the low and highindex layers 50, 52 are within the range of about 10 nm to about 1000nm. Optionally, either the high or low index films 50, 52 may have thealternating high and low physical densities, the goal being the netreduction in overall optical coating stress.

During manufacture, to prevent typical damage to the sensitiveunderlying semiconductor surface, a first layer 54 of a low density, lowindex material may be deposited on the sensitive surface of thesemiconductor body 42. This first layer 54 may have a thickness of about150 nm to about 800 nm. For example, the first layer 54 may have athickness of about >200 nm. Thereafter, multiple alternating layers oflow index materials 50 and high index materials 52 may be selectivelyapplied thereto. Once the multiple layers of low and high indexmaterials 50, 52 are applied, the optically coated device 40 may befurther processed using a combination of chemical processing (e.g.hydrofluoric acid) and/or physical processing (e.g. ion beam milling)until this first layer 54 and/or semiconductor body 42 is exposed. Ifneeded, the first layer 54 may be further processed using anon-damaging, gentle, controlled chemical etching process. Due to itslow-density structure, the first layer 54 etches easily with therequired geometric precision demanded without any risk of damage to thesensitive underlying semiconductor surface. If desired, subsequentdevice processing (after the desired section of coating is fullyremoved), may include application of additional filter layers, formingdiscreet filtering sections within the multiple layer coating (SEE FIG.9), and/or the deposition of a conductor device 56 (e.g. aluminum,titanium/gold, etc) used for electrically coupling the semiconductordevice 40 to an energy source (as for an LED) or to an outsideelectrical circuit (as for a detector).

FIGS. 8 and 9 show alternate embodiment of the semiconductor deviceshown in FIG. 7. As stated above, the semiconductor device may comprisea single detector device or multiple detector devices. For example, FIG.8 shows an embodiment of a multiple detector semiconductor device 60having a body 62 defining multiple detector regions 64 a-64 n. Forexample, each detector may be configured to detect optical radiation atthe same wavelength or different wavelengths. For example, detectorregion 64 a may be configured to detect radiation having a wavelengthbetween about 400 nm and about 450 nm, while detector region 64 b isconfigured to detect radiation having a wavelength of about 450 nm toabout 500 nm. Referring again to FIG. 8, a multiple layer optical filtercoating 66 as described above may be uniformly applied to thesemiconductor device 60. The multiple layer coating 66 may be configuredto reflect radiation having a wavelength greater than or less thanradiation at a predetermined wavelength range.

FIG. 9 shows an alternate embodiment of a multiple detectorsemiconductor device. Like the previous embodiment, the semiconductordevice 70 includes a body 72 defining multiple detector regions 74 a-74n. In contrast to the previous embodiment, the multiple layer coating 76formed as described above defines multiple filtering regions 78 a-78 n.Each filtering region 78 a-78 n may correspond to a specific detectorregion 74 a-74 n. As such, each filtering region 78 a-78 n may beconfigured to selectively filter radiation within prescribed wavelengthrange. In one embodiment, the filtering regions 78 a-78 n may be formedbe by controllable varying the number, density, composition, and/orthickness of the various layers forming the multiple layer opticalfilter coating.

Example

An exemplary device was constructed using the process described above.In this embodiment, a multilayer optical coating was applied directlyonto a silicon wafer (having photovoltaic devices processed onto itssurface). The multilayer optical coating was configured to filter theincident light energy by transmitting a desired spectral band andrejecting light outside of this region. As such, only light within thespectral band 600 nm+/−5 nm was transmitted through the optical coatingand subsequently detected by the semiconductor device. The physicalcharacteristics of the coatings are as follows:

SILICON WAFER/220 L 49.59 H 114.91 L (64.18 H 209.35 L 64.18 H 104.68L)7 128.35 H 104.68 L 64.18 H 104.68 L 64.18 H 104.68 L 256.7 H 104.68 L64.18 H 104.68 L 64.18 H 104.68 L 64.18 H 104.68 L 64.18 H 104.68 L385.06 H 104.68 L 64.18 H 104.68 L 64.18 H 104.68 L 64.18 H 104.68 L64.18 H 104.68 L 256.7 H 104.68 L 64.18 H 104.68 L 64.18 H 104.68 L112.28 H 72.02 L/AIR

Where the symbols L and H signify the physical thicknesses (in nm) of L(low index) and H (high index) thin films. The low index materialcomprised silicon dioxide, while the high index material comprisedniobium dioxide.

FIG. 10 shows graphically the reflectance characteristics of the opticalcoating applied to the exemplary device, while FIG. 11 shows thetransmittance of the optical coating applied to the exemplary device.

In this example, the layers designated “L” are low-density, poroussilicon dioxide films deposited by conventional physical vapordeposition methods (electron beam evaporated silicon dioxide oroxygen-plasma converted silicon monoxide evaporated by a resistivesource). The first layer is of a thickness of 220 nm, which allows forthe subsequent final device processing etching step using hydrofluoricacid. Encapsulating alternating high-density, high index H films aredeposited by plasma-assisted magnetron sputtering (niobium dioxide). Asillustrated in FIG. 7, the complete optical coating is etched inselected areas for contact metallization using the aforementionedmethods. The final spectral responsivity of the optically coated siliconphoto detector is illustrated in FIG. 11.

With regard to the above detailed description, like reference numeralsused therein refer to like elements that may have the same or similardimensions, materials and configurations. While particular forms ofembodiments have been illustrated and described, it will be apparentthat various modifications can be made without departing from the spiritand scope of the embodiments of the invention. Accordingly, it is notintended that the invention be limited by the forgoing detaileddescription.

What is claimed is:
 1. A method of manufacturing an optically coatedsemiconductor device, comprising: forming a low-stress, low densityporous columnar film structure on a surface of a semiconductor device bydepositing a first layer of a low density, low index of refractionmaterial on the surface of the semiconductor device; depositing amulti-layer optical coating comprising alternating layers of lowdensity, low index of refraction materials and high density, high indexof refraction materials on the coated surface of the semiconductordevice; selectively ablating a portion of the alternating multi-layeroptical coating to expose at least a portion of the low density firstlayer using a first ablation process; and selectively ablating a portionof the first layer of low density material to expose at least a portionof the semiconductor device using a second ablation process.
 2. Themethod of claim 1 wherein at least one low density, low index ofrefraction material is applied using a resistive-source evaporationprocess.
 3. The method of claim 1 wherein at least one low density, lowindex of refraction material is applied using a conventionalelectron-beam deposition process.
 4. The method of claim 1 wherein atleast one high density, high index of refraction material is appliesusing a magnetron sputtering process.
 5. The method of claim 1 whereinat least one high density, high index of refraction material is appliesusing an ion-beam sputtering processes.
 6. The method of claim 1 whereinat least one high density, high index of refraction material is appliesusing a cathodic-arc deposition process.
 7. The method of claim 1wherein at least one high density, high index of refraction material isapplies using an ion-assisted electron-beam deposition process.
 8. Themethod of claim 1 wherein at least one high density, high index ofrefraction material is applies using an ion-plating process.
 9. Themethod of claim 1 wherein the multi-layer optical coating is selectivelyablated using physical ablating processes.
 10. The method of claim 9wherein the physical ablating process comprises ion beam milling. 11.The method of claim 1 wherein the multi-layer optical coating isselective ablated using chemical ablating processes.
 12. The method ofclaim 11 wherein the chemical ablating process comprises hydrofluoricacid processing.
 13. The method of claim 1 wherein the first layer isablated using a controlled chemical etching process.
 14. A method ofmanufacturing an optically coated semiconductor device, comprising:forming a low-stress, low density porous columnar film structure on asurface of a semiconductor device by depositing a first layer of a lowdensity, low index of refraction material on the surface of thesemiconductor device; depositing a multi-layer optical coatingcomprising alternating layers of low density, low index of refractionmaterials and high density, high index of refraction materials on thecoated surface of the semiconductor device; selectively ablating aportion of the alternating multi-layer optical coating using a physicalablation process to expose at least a portion of the low density firstlayer; and selectively ablating a portion of the first layer of lowdensity material using a controlled chemical etching process to exposeat least a portion of the semiconductor device.
 15. The method of claim14 wherein at least one low density, low index of refraction material isapplied using a resistive-source evaporation process.
 16. The method ofclaim 14 wherein at least one low density, low index of refractionmaterial is applied using a conventional electron-beam depositionprocess.
 17. The method of claim 14 wherein at least one high density,high index of refraction material is applies using a magnetronsputtering process.
 18. The method of claim 14 wherein at least one highdensity, high index of refraction material is applies using an ion-beamsputtering processes.
 19. The method of claim 14 wherein at least onehigh density, high index of refraction material is applies using acathodic-arc deposition process.
 20. The method of claim 14 wherein atleast one high density, high index of refraction material is appliesusing an ion-assisted electron-beam deposition process.
 21. The methodof claim 14 wherein at least one high density, high index of refractionmaterial is applies using an ion-plating process.
 22. The method ofclaim 14 wherein the physical ablating process comprises ion beammilling.